Camera shaking correcting method, camera shaking correcting device, and image pickup device

ABSTRACT

Output of a gyro sensor is read at intervals of control time ts, time integration is carried out, an integrated value is computed, and an amount of change in an integrated value is determined from a difference between the calculated integrated value and an integrated value of a previous time. Thereafter, on the basis of the amount of change and a delay time determined by a shaking correcting module and the control time, an addition value (an acceleration value of an integrated value of the current time) is computed in order to obtain an amount of movement of a shift lens which can compensate tilting of an optical axis of a lens. After the computed addition value is added to the integrated value of the current time, a control value for moving the shift lens is computed by using the integrated value after addition.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 from Japanese PatentApplication Nos. 2004-329004 and 2004-341504, the disclosures of whichare incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image pickup device such as adigital still camera, a digital video camera, or the like which obtainsimage data corresponding to a photographed image, and in particular,relates to a camera shaking correcting method of an image pickup deviceequipped with an optical-type camera shaking correcting function, and toa camera shaking correcting device and an image pickup device.

2. Description of the Related Art

Of course among digital video cameras, digital still cameras, and thelike, and among silver salt photographic cameras and the like as well,there are cameras equipped with a camera shaking correcting functionwhich corrects blurring of a photographed image due to so-called camerashaking. The provision of a camera shaking correcting function isbecoming standard in higher-end cameras.

Camera shaking correcting functions include electronic-type blurringcorrection in which, in accordance with shaking which is detected byusing the correlation with an image, the data reading position from animage pickup element such as a CCD or from image data expanded in amemory is controlled, so that blurring caused by camera shaking does notarise in the photographed image. In addition, there is optical-typeblurring correction in which, by using a sensor (e.g., a gyro sensor)detecting the acceleration, angular acceleration, angular velocity orthe like of the device main body, the center of the lens is shiftedalong a direction orthogonal to the optical axis on the basis of anoutput signal from the sensor, and by correcting the offset of theoptical axis by changing the inclination of the incident light withinthe lens, the effects of shaking which appear on the image pickupelement due to camera shaking are compensated (offset).

An optical-type camera shaking correcting mechanism uses a gyro sensorwhich works semi-independently of a signal processing system, and fromoutput of the gyro sensor which is sampled at an arbitrary period,computes an amount of movement of the image caused by blurring,determines a shift amount of the lens, and controls an actuator so as tothereby shift the optical axis.

At this time, shaking which arises due to rotation of the overall deviceis detected as a time-series change in the rotational velocity at apredetermined sampling interval by an angle sensor. Because thistime-series information is the rotational velocity at each samplingtime, correction angle information is obtained by carrying outintegration processing using the sampling period as the time unit, bycumulative integration (successive addition).

Further, by sending this integrated value to a driving circuit asinformation specifying the lens position, the driving circuit moves apredetermined lens on the basis of this integrated value. In this way,shaking of the image of the subject of photographing, which is imaged onthe image pickup element, i.e., the generation of changes in the imagingposition, is suppressed (see, for example, Japanese Patent ApplicationLaid-Open (JP-A) Nos. 63-8628 and 8-101418).

Because optical-type blurring correction compensates changes in theimage angle of the device main body by optical axis rotation, if thereis a time delay (time lag) from the detection of the shaking of the mainbody to the lens control, shaking amount corresponding to that delaytime will appear as blurring of the image which is imaged at the imagepickup element, and the quality of the photographed image willdeteriorate.

Because it is difficult to eliminate the delay time, there have beenproposals to make the effects of a delay time substantially not bemanifested, by carrying out correction processing using optimalparameters corresponding to the shaking, by judging the shakingfrequency and switching parameters which are set for each shakingfrequency (see, for example, JP-A No. 6-98246).

Further, there have also been proposals to make blurring not arise in aphotographed image by judging a shaking waveform from time-seriesinformation, estimating a shaking amount at a prescribed time in thefuture, and carrying out shaking correction on the basis of the resultsof estimation (see, for example, JP-A Nos. 5-204013 and 5-204014).

However, in these methods, there is the need to analyze the shakingfrequency components, or carry out computation processing by the methodof least squares or the like such that the time-series data of thecamera shaking vibrations approximates a high-order regression curveline, and judge the main frequency of the shaking. To this end,complicated computation processing utilizing a large amount of data isnecessary, and a system having a high computational capacity must beused or a long computing time is required.

This therefore leads to an increase in the size of and an increase inthe cost of the pickup device, and substantial elimination of blurringis difficult.

On the other hand, an angular velocity sensor which is used in detectingshaking utilizes a method of sensing the torsional force of thevibrating object. Therefore, the detection sensitivity is low.Accordingly, when the torsional force is extracted as time-seriesinformation of the rotational velocity, it must be amplified. Thus, itis easy for fluctuations in output to arise due to affects such as noiseor drift of the DC or the like due to the temperature characteristic orthe like, and as a result, it is easy for the shaking correcting deviceto function erroneously.

A general output circuit 202 using angular velocity sensors 200A, 200Bis shown in FIG. 19A. An HPF (High-Pass Filter) 206 using alarge-capacity capacitor 204 is structured in this output circuit 202.By the HPF 206, the DC components of the angular velocity sensors 200A,200B are cut-off, and a predetermined bias voltage is applied at anamplifying circuit 208. In this way, signals (a PITCH signal and a YAWsignal), in which the occurrence of errors due to drift and the DCcomponent are suppressed, are outputted.

On the other hand, low frequency components of around 1 Hz also areincluded in the frequency components of the shaking. Therefore, if theDC component removal by the HPF 206 is made to be great, the lowfrequency camera shaking components are damped, and a sufficient camerashaking correcting effect cannot be obtained.

In order to prevent this, the time constant at the HPF 206 must be madeto be long (e.g., greater than or equal to 10 sec), but, by doing this,the effect of reducing the drift deteriorates. Namely, it is difficultto simultaneously achieve both drift reduction and precise shakingdetection of low frequencies at the output circuit of the angularvelocity sensor.

As a method of overcoming this problem, drift reduction is aimed for asfollows: a reference value which follows fluctuations in input isdetermined by using a cyclic filter of a long period on the numericaldata obtained by A/D converting and sampling the sensor output (theoutput of the output circuit) with the time constant of the HPF beingmade to be 10 sec or more, and this reference value is subtracted fromthe input signal.

FIG. 19B shows the schematic structure of a general cyclic filter 210.In this cyclic filter 210, given that a transfer coefficient of aregister 212 is n, an input signal is Sin, and an output signal(reference value) is Sout, the reference value Sout is:Sout=Sin×(1−n)+Sout×nand the drift component is extracted as a difference between thereference value Sout and the input signal Sin.

However, drift following which uses such a cyclic filter has a high bandpass limiting (LPF) characteristic with respect to the input signal.Therefore, with respect to high-frequency shaking, the correction valueis damped. Further, a detection signal in which the high-frequencycomponents are damped has an HPF characteristic in which the higher thefrequency, the greater the amplitude, which is opposite of the referencevalue which is the output of the cyclic filter.

In this way, the level of the correction value obtained by integratingthe detection value differs in accordance with the frequency, and theproblem arises that an optimal correction level can be obtained onlywith respect to vibrations of specific frequencies.

SUMMARY OF THE INVENTION

The present invention was developed in view of the aforementioned, andprovides a camera shaking correcting method, a camera shaking correctingdevice, and an image pickup device which can suppress the occurrence ofblurring in a photographed image by simple computation processing.

Further, the present invention provides a camera shaking correctingdevice and an image pickup device in which a substantially uniformcharacteristic can be obtained regardless of the frequency, and whichaim for reliable reduction in drift, and which enable highly-accurateshaking correction.

A first aspect of the present invention provides a method of correctingcamera shaking which, in an image pickup device outputting image datacorresponding to an image of a subject of photographing which is imagedby a lens on an image pickup element of the device, corrects, bymovement of a lens, tilting of an optical axis due to shaking of ahousing of the device, the method including: detecting, at apredetermined control time interval, an angular velocity at a time whenshaking of the housing arises; on the basis of a time integrated valueof the detected angular velocity, setting an amount of movement of thelens which compensates the tilting of the optical axis due to shaking ofthe housing, the setting including adding an addition value, which isbased on a difference between a time integrated value of the currenttime and a time integrated value of a previous time and on a delaycoefficient set from a phase delay and the control time, to the timeintegrated value of the current time; and moving the lens on the basisof a control value obtained from results of the adding.

In accordance with this invention, the angular velocity due to vibrationsuch as shaking or the like is read at a predetermined control timeinterval. The control value at the time of moving the lens is computedby using the time integrated value computed by carrying out timeintegration at each control time.

At this time, the addition value is computed on the basis of thedifference between the time integrated value of the current time and thetime integrated value of the previous time, and the phase delay and thecontrol time. The control value is computed on the basis of the timeintegrated value of the current time to which this addition value hasbeen added.

For the addition value at this time, the necessary addition value isdetermined from the difference in the time integrated values, the delaytime and the control time. Therefore, the calculation formulas can beset in advance such that this addition value is obtained.

In this way, the lens can be moved such that the tilting of the opticalaxis due to vibration of the housing is compensated (offset), withoutcarrying out complex computing processing.

As a device for correcting camera shaking to which the present inventionis applied, a second aspect of the present invention provides a devicefor correcting camera shaking which corrects, by movement of a lens,tilting of an optical axis due to shaking of a housing of an imagepickup device which outputs image data corresponding to an image of asubject of photographing which is imaged by a lens on an image pickupelement of the image pickup device, the device for correcting camerashaking including: a vibration detecting section detecting shaking ofthe housing, and outputting a signal corresponding to the shaking; anintegration processing section reading a detection signal of thevibration detecting section at a predetermined control time interval,and computing a time integrated value; a computing section storing atime integrated value of the integration processing section, andcomputing an addition value for the time integrated value, on the basisof a difference between the time integrated value and a time integratedvalue of a previous time, and a delay coefficient set from a phase delayand the control time; a setting section setting an amount of movement ofthe lens from the integrated value to which the addition value has beenadded by the computing section; and a lens driving section moving theoptical axis of the lens on the basis of the amount of movement set bythe setting section.

As an image pickup device to which the present invention is applied, athird aspect of the present invention provides an image pickup deviceoutputting image data corresponding to an image of a subject ofphotographing which is imaged by a lens on an image pickup element ofthe device, the image pickup device including: a vibration detectingsection detecting shaking of a housing which houses the lens and theimage pickup element, and outputting a signal corresponding to theshaking; an integration processing section reading a detection signal ofthe vibration detecting section at a predetermined control timeinterval, and, computing a time integrated value; a computing sectionstoring a time integrated value of the integration processing section,and computing an addition value for the time integrated value, on thebasis of a difference between the time integrated value and a timeintegrated value of a previous time, and a delay coefficient set from aphase delay and the control time; a setting section setting an amount ofmovement of the lens from the integrated value to which the additionvalue has been added by the computing section; and a lens drivingsection moving an optical axis of the lens on the basis of the amount ofmovement set by the setting section.

A fourth aspect of the present invention provides a device forcorrecting camera shaking provided at an image pickup device whichoutputs image data corresponding to a photographed image which haspassed through a lens housed in a housing of the image pickup device andwhich is imaged on an image pickup element of the image pickup device,the device for correcting camera shaking including: an angular velocitydetecting section detecting an angular velocity due to shaking arisen atthe housing; an integration computing section computing an integratedvalue corresponding to a change in an angle of an optical axis of thelens due to shaking, by time integrating at a predetermined timeinterval an angular velocity signal outputted from the angular velocitydetecting section; a control value setting section which, on the basisof an integrated value outputted from the integration computing section,sets a control value for obtaining a correction angle needed in order tocompensate tilting of the optical axis of the lens due to the shaking; alens driving section which, on the basis of the control value set by thecontrol value setting section, drives the lens so as to tilt the opticalaxis of the lens; and a filter processing section which extracts areference value from the angular velocity signal detected by the angularvelocity detecting section, and outputs a difference between thedetected angular velocity signal and the reference value to theintegration computing section as a corrected angular velocity signal,the filter processing section extracting the reference value from anangular velocity signal to which a preset constant value has been addedor subtracted on the basis of results of comparison of the referencevalue and an angular velocity signal inputted from the angular velocitydetecting section.

In accordance with the present aspect, an angular velocity signal, whichis corrected by subtracting the reference value from the angularvelocity signal outputted from the angular velocity detecting section,is outputted. At this time, a constant value is set in advance, and thepositive/negative sign of the corrected angular velocity signal isjudged. By adding or subtracting the constant value to or from thereference value on the basis of the results of judgment, the referencevalue is updated.

By using the reference value which has been updated in this way, it ispossible to obtain an angular velocity signal in which the DC componenthas been precisely extracted from the inputted angular velocity signal.

By using this angular velocity signal, appropriate shaking correction ispossible, and it is possible to precisely suppress blurring from arisingin the photographed image.

In the present aspect, the filter processing section may add theconstant value to the angular velocity signal when the level of theangular velocity signal is greater than the level of the referencevalue, and subtract the constant value from the angular velocity signalwhen the level of the angular velocity signal is smaller than the levelof the reference value.

A fifth aspect of the present invention provides a device for correctingcamera shaking provided at an image pickup device which outputs imagedata corresponding to a photographed image which has passed through alens housed in a housing of the image pickup device and which is imagedon an image pickup element of the image pickup device, the device forcorrecting camera shaking including: an angular velocity detectingsection detecting an angular velocity due to shaking arisen at thehousing; an integration computing section computing an integrated valuecorresponding to a change in an angle of an optical axis of the lens dueto shaking, by time integrating at a predetermined time interval anangular velocity signal outputted from the angular velocity detectingsection; a control value setting section which, on the basis of anintegrated value outputted from the integration computing section, setsa control value for obtaining a correction angle needed in order tocompensate tilting of the optical axis of the lens due to the shaking; alens driving section which, on the basis of the control value set by thecontrol value setting section, drives the lens so as to tilt the opticalaxis of the lens; and an integrated value filter processing sectionwhich is provided at the control value setting section, and whichcorrects an integrated value used in setting the control value by addingor subtracting a preset constant value to or from the integrated valuein accordance with a positive/negative sign of the integrated valueoutputted from the integration computing section.

In accordance with the present aspect, when setting the control valueused at the lens driving section from the integrated value obtained byintegrating the angular velocity signal outputted from the angularvelocity detecting section, the reference value is subtracted from theintegrated value. At this time, the constant value is set in advance.The positive/negative sign of the integrated value, from which thereference value has been subtracted, is judged. By adding or subtractingthe constant value to or from the reference value on the basis of theresults of this judgment, the reference value is updated.

By using the reference value which has been updated in this way, it ispossible to obtain an integrated value in which the DC component withinthe angular velocity signal is precisely extracted from the integratedvalue obtained by the integration processing, and it is possible toprevent the integrated value from converging at a high frequency aswell.

Accordingly, appropriate shaking correction based on the results ofdetection of the angular velocity detecting section is possible, andblurring arising in the photographed image can be precisely suppressed.

In the present aspect, the integrated value filter processing sectionmay subtract the constant value from the integrated value when theintegrated value is positive, and may add the constant value to theintegrated value when the integrated value is negative.

A sixth aspect of the present invention provides an image pickup devicewhich outputs image data corresponding to a photographed image which haspassed through a lens housed in a housing of the device and which isimaged on an image pickup element of the device, the image pickup deviceincluding: an angular velocity detecting section detecting an angularvelocity due to shaking arisen at the housing; a filter processingsection which extracts a reference value from the angular velocitysignal detected by the angular velocity detecting section, and outputs adifference between the detected angular velocity signal and thereference value as a corrected angular velocity signal, the filterprocessing section extracting the reference value from an angularvelocity signal to which a preset constant value has been added orsubtracted on the basis of results of comparison of the reference valueand an angular velocity signal inputted from the angular velocitydetecting section; an integration computing section computing anintegrated value corresponding to a change in an angle of an opticalaxis of the lens due to the shaking, by time integrating at apredetermined time interval the angular velocity signal corrected by thefilter processing section; a control value setting section which, on thebasis of the integrated value outputted from the integration computingsection, sets a control value for obtaining a correction angle needed inorder to compensate tilting of the optical axis of the lens due to theshaking; and a lens driving section which, on the basis of the controlvalue set by the control value setting section, drives the lens so as totilt the optical axis of the lens.

A seventh aspect of the present invention provides an image pickupdevice which outputs image data corresponding to a photographed imagewhich has passed through a lens housed in a housing of the device andwhich is imaged on an image pickup element of the device, the imagepickup device including: an angular velocity detecting section detectingan angular velocity due to shaking arisen at the housing; an integrationcomputing section computing an integrated value corresponding to achange in an angle of an optical axis of the lens due to shaking, bytime integrating at a predetermined time interval an angular velocitysignal outputted from the angular velocity detecting section; anintegrated value filter processing section which corrects the integratedvalue by adding or subtracting a preset constant value to or from theintegrated value, in accordance with a positive/negative sign of theintegrated value outputted from the integration computing section; acontrol value setting section which, on the basis of the integratedvalue corrected by the integrated value filter processing section, setsa control value for obtaining a correction angle needed in order tocompensate tilting of the optical axis of the lens due to the shaking;and a lens driving section which, on the basis of the control value setby the control value setting section, drives the lens so as to tilt theoptical axis of the lens.

As described above, in accordance with the present invention, tilting ofthe optical axis of a lens due to shaking of a housing can beappropriately corrected by a simple computation processing such asfour-rule computation or the like. In this way, there is the excellenteffect of providing an image pickup device which enables high-qualityimage photographing without blurring at a low cost.

Further, the drift component can be precisely extracted by simpleprocessing from the angular velocity signal outputted from the angularvelocity detecting section, and accurate camera shaking correction ispossible.

In this way, there are the excellent effects that blurring and the likeare reliably prevented from arising in a photographed image which isphotographed by the image pickup device, and a high-quality photographedimage can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described in detail basedon the following figures, wherein:

FIG. 1 is a schematic external view of a digital camera applied toembodiments;

FIG. 2 is a block diagram showing the schematic structure of mainportions of the digital camera;

FIG. 3 is a block diagram showing the schematic structure of a shakingcorrecting module applied to a first embodiment;

FIG. 4 is a graph showing an outline of the times of changes in angularvelocity output, integrated value output, correction amount output, andlens driving, with respect to vibration of a housing;

FIG. 5 is a flowchart showing an outline of computation processing of ashaking correcting amount (control value);

FIG. 6 is a schematic diagram showing changes in an optical axis due toshaking, and changes in an optical axis due to shaking correction;

FIG. 7 is a schematic structural diagram of a shaking correcting moduleapplied to a second embodiment;

FIG. 8A is graph showing an outline of an amplitude range of an angularvelocity signal which does not contain a drift component, FIG. 8B is agraph showing an outline of an amplitude range of an angular velocitysignal which contains a drift component, and FIG. 8C is a graph showingan outline of an amplitude range of an angular velocity signal when adrift component is not considered;

FIG. 9 is a graph showing an outline of a drift component, an angularvelocity signal which contains a drift component, and an angularvelocity signal which does not contain a drift component;

FIG. 10A is a schematic structural diagram of a filter circuit appliedto the second embodiment, FIG. 10B is a graph showing an example of aninput signal, and FIG. 10C is a graph showing a summary of changes in areference value at the filter circuit shown in FIG. 10A at the time ofthe input signal of FIG. 10B;

FIG. 11A is a schematic structural diagram of a filter circuit which isa comparative example of FIG. 10A, FIG. 11B is a graph showing anexample of an input signal, and FIG. 11C is a graph showing a summary ofchanges in a reference value at the filter circuit shown in FIG. 11A atthe time of the input signal of FIG. 11B;

FIGS. 12A through 12C are graphs showing results of measurement at atime of using the filter circuit of FIG. 11A;

FIGS. 13A through 13C are graphs showing results of measurement at atime of using the filter circuit of FIG. 12A;

FIG. 14 is a flowchart of processings which can be applied instead of afilter circuit in the second embodiment;

FIG. 15 is a schematic structural diagram of a shaking correcting moduleapplied to a third embodiment;

FIG. 16A is a schematic structural diagram of a filter circuit appliedto the third embodiment, FIG. 16B is a graph showing an example of aninput signal, and FIG. 16C is a graph showing a summary of changes in areference value at the filter circuit shown in FIG. 16A at the time ofthe input signal of FIG. 16B;

FIG. 17A is a schematic structural diagram of a filter circuit which isa comparative example of FIG. 16A, FIG. 17B is a graph showing anexample of an input signal, and FIG. 17C is a graph showing a summary ofchanges in a reference value at the filter circuit shown in FIG. 17A atthe time of the input signal of FIG. 17B;

FIG. 18 is a flowchart of processings which can be applied instead of afilter circuit in the third embodiment; and

FIG. 19A is a schematic wiring diagram of main portions showing ageneral output circuit, and FIG. 19B is a schematic structural diagramshowing an example of a general cyclic filter.

DETAILED DESCRIPTION OF THE INVENTION

Examples of embodiments of the present invention will be described indetail hereinafter with reference to the drawings. FIG. 1 shows theschematic structure of the exterior of a digital still camera(hereinafter called “digital camera”) 10 which is applied to theembodiments as an image pickup device.

The digital camera 10 has a lens 12 for imaging an image of a subject ofphotographing, a finder 14 for deciding upon the composition of thesubject to be photographed, a release button (so-called “shutterbutton”) 16 depressed at the time of photographing, a power switch 18,and the like. At the digital camera 10, two stages of the operation ofdepressing the release button 16 are possible, which are ahalf-depressed state in which the release button 16 is depressed to anintermediate position, and a fully-depressed state in which the releasebutton 16 is depressed past the intermediate position to a finalposition.

Provided at the back surface of the digital camera 10 are a liquidcrystal display (hereinafter called “LCD”) 20 used in displaying theimage of the subject of photographing which corresponds to digital imagedata obtained by photographing, as well as various types of menuscreens, messages, and the like; a photographing switch 22 operated atthe time of setting a photographing mode and the mode (static image modeor dynamic image mode) at the time of the photographing mode; a playbackswitch 24 operated at the time of setting a playback mode which displaysthe photographed image on the LCD 20; a cross cursor button 26 operatedwhen a menu screen is displayed on the LCD 20; a zoom button 28 operatedat the time of carrying out zooming (enlargement and reduction) of theimage of the subject of photographing at the time of photographing; andthe like.

A receptacle 30, which can be connected to an external device by apredetermined interface standard such as USB (Universal Serial Bus) orthe like, is provided at the bottom surface of the digital camera 10.Note that a self-timer LED 34, which, by a flashing interval, givesnotice of the arrival of the time of photographing when carrying outimage photographing by using a self-timer function, and the like may beprovided at the digital camera 10. Further, a DC terminal 36, which isfor enabling the supply of electric power for operation from theexterior, and the like, may be provided at the digital camera 10.

When the static image mode (static image photographing mode) is set atthe digital camera 10, due to the release button 16 being set in thehalf-depressed state, an AE (Automatic Exposure) function works, and theexposure state, such as the shutter speed, the state of the diaphragm,and the like, is set. Thereafter, an AF (Auto Focus) function works suchthat the focus is controlled. Moreover, image exposure (imagephotographing) is carried out by the release button 16 being set in thefully-depressed state in continuation from the half-depressed state.

When the dynamic image mode (dynamic image photographing mode) is set atthe digital camera 10, dynamic image photographing is started by therelease button 16 being set in the fully-depressed state. After therelease button 16 is returned from the fully-depressed state to thehalf-depressed state, the dynamic image photographing is stopped by therelease button 16 again being set in the fully-depressed state. Notethat conventionally-known methods can be used for the automatic exposurefunction and the focus control and the like, and detailed descriptionthereof is omitted in the embodiments. Further, the operations of theimage pickup device to which the present invention is applied are notlimited to these.

The schematic structure of main portions of the digital camera 10 isshown in FIG. 2. The lens 12, which collects the light from the subjectof photographing within a housing 38 (see FIG. 1), and an image pickupelement 40, which uses a CCD, a CMOS image sensor or the like, areprovided at the digital camera 10.

The lens 12 is formed so as to include, for example, a fixed lens 12A, azoom lens 12B which changes the magnification, a focus lens 12C whichhas a function for correcting movement of a focal plane and adjustingthe focal point accompanying a change in magnification, and the like.Note that, in FIG. 2, the diaphragm, the shutter, and the like areomitted from illustration.

In accordance with this structure, at the digital camera 10, the imageof the subject of photographing is imaged on the image pickup element 40by the light collected by the fixed lens 12A, and an electric signal(analog image signal) corresponding to the amount of received light ofeach pixel is outputted from the image pickup element 40.

An amplifying section 42 is provided at the digital camera 10. Theamplifying section 42 amplifies the analog signals outputted from theimage pickup element 40.

A signal processing section 44 is structured at the digital camera 10 byusing an image processing system IC or the like equipped with amicrocomputer having a CPU, a ROM, a RAM, a data bus, a system bus, andthe like, which are not illustrated.

At the signal processing section 44, due to A/D conversion being carriedout on the analog signals inputted from the amplifying section 42,digital image data corresponding to the photographed image (the image ofthe subject of photographing) is generated. At this time, at the signalprocessing section 44, the signals of R (red), G (green) and B (blue)are converted into, for example, 12-bit R, G, B signals.

Further, at the signal processing section 44, white balance adjustmentis carried out by multiplying the image data, which was generated by theA/D conversion, by a digital gain corresponding to the type of the lightsource. Further, γ processing, sharpness processing, and the like arecarried out, so as to generate, for example, 8-bit image data. Moreover,at the signal processing section 44, YC signal processing is carried outon the image data so as to generate a luminance signal Y and chromasignals Cr, Cb (YC signals).

The YC signals are stored in an image buffer (not shown), and can beused when an image is displayed on the LCD 20. In this way, athrough-image can be displayed on the LCD 20.

Here, when static image photographing mode is set and the release button16 is depressed (fully depressed), the YC signals are compressed in apredetermined compression format such as JPEG or the like at the signalprocessing section 44, and outputted as an image file of thephotographed image.

The image file outputted from the signal processing section 44 isrecorded on a recording medium (e.g., a SmartMedia, IC card, CD-R,CD-RW, or the like) loaded in the digital camera 10. Further, the imagefiles outputted from the signal processing section 44, and image filesrecorded on the recording medium, can be outputted via the receptacle 30to a personal computer (PC), a TV, or the like.

When dynamic image photographing mode is set, due to the release button16 being fully depressed, dynamic image photographing is started. Afterthe release button 16 is returned to its half-depressed state, duringthe period of time until it is fully depressed, i.e., during the periodof time in which photographing of the dynamic image is carried out, theYC signals stored in the unillustrated image buffer are compressed in apredetermined format (e.g., Motion JPEG or the like) in eachpredetermined time (e.g., a time which is set in advance such as each1/30 second or the like), and outputted as an image file of a dynamicimage.

In the digital camera 10 which is structured in this way, due to thepower switch 18 being turned on and the photographing switch 22 beingoperated, the subject is imaged on the image pickup element 40 by thelens 12.

The image pickup element 40 outputs data corresponding to the image ofthe subject of photographing which has been imaged. This data issubjected to amplification processing, and thereafter, is A/D converted,and the data is thereby read by the signal processing section 44 asimage data.

At the signal processing section 44, by subjecting this image data topredetermined processings, the image data can be displayed on the LCD20. Further, by operating the release button 16 and carrying out imagephotographing, the image file of the photographed image is outputtedfrom the signal processing section 44.

At the digital camera 10, when vibrations arise at the housing 38 due tocamera shaking or the like, tilting arises at the optical axis of thelens 12 with respect to the subject of photographing, and offset arisesin the position of the subject of photographing which is imaged on theimage pickup element 40. Such offset becomes blurring of thephotographed image, and deterioration of the quality of the photographedimage arises.

In order to prevent such blurring of the photographed image, the digitalcamera 10 is equipped with a shaking correcting function which carriesout camera shaking correction by an optical method. Here, the shakingcorrecting function provided at the digital camera 10 will be describedas an embodiment of the present invention.

As shown in FIG. 2, a shaking correcting module 50, which carries outcamera shaking correction by an optical method, is provided at thedigital camera 10. The shaking correcting module 50 has a gyro sensor 52(shaking detecting means) which is provided as an angular velocitydetecting section which detects angular velocity at the time when thehousing 38 (see FIG. 1) shakes.

A correction computing section 54 and a lens driving circuit 56 areprovided at the shaking correcting module 50. A shift lens 58 isprovided at the lens 12. The shift lens 58 is shifted by the lensdriving circuit 56 in two directions which are orthogonal to the opticalaxis of the lens 12 (e.g., when the optical axis is horizontal, the twodirections are the vertical direction and the horizontal direction whichis orthogonal to both the vertical direction and the optical axis, andhereinafter, in order to simplify explanation, the vertical directionand horizontal direction are referred as to these two directions).

First Embodiment

As shown in FIG. 3, the gyro sensor 52 has a vertical angular velocitysensor 52A and a horizontal angular velocity sensor 52B. The verticalangular velocity sensor 52A and the horizontal angular velocity sensor52B detect the angular velocity in the vertical direction and theangular velocity in the horizontal direction of the digital camera 10,and output signals corresponding to the detected angular velocities.Note that, instead of the angular velocity sensors, acceleration sensorsor angular acceleration sensors or the like may be used.

The outputs of the gyro sensor 52 are inputted to the correctioncomputing section 54 via an amplifying circuit (Amp) 60 and an A/Dconverter 62. The correction computing section 54 has a microcomputer(not shown), and an integration computing section 64 (integrationprocessing section) and a correction amount computing section 66 areformed thereby.

Due to the lens driving circuit 56 driving an actuator (not illustrated)on the basis of a blurring correction amount outputted from thecorrection amount computing section 66, the shift lens 58 moves in thevertical direction and the horizontal direction.

Due to the shift lens 58 being shifted, the optical axis of the lens 12of the digital camera 10 is tilted in the vertical direction and thehorizontal direction. In this way, the position of the image of thesubject of photographing which is imaged on the image pickup element 40is shifted.

After the shaking correcting module 50 amplifies the output signals(angular velocity signals) of the vertical angular velocity sensor 52Aand the horizontal angular velocity sensor 52B, the shaking correctingmodule 50 converts the signals into digital data, and inputs the digitaldata to the integration computing section 64. At the integrationcomputing section 64, due to the output signals of the vertical angularvelocity sensor 52A and the horizontal angular velocity sensor 52B beingtime integrated, the angular velocity, which is the integrated value ofthe vertical direction and horizontal direction angle changes perpredetermined time period, is computed. Note that, at the shakingcorrecting module 50, before the A/D conversion is carried out, the DCcomponents are removed by carrying out band limiting by using anunillustrated HPF (High-Pass Filter) or the like.

At the correction amount computing section 66, a control value, which isa correction amount for moving the shift lens 58, is computed on thebasis of the results of integration (the integrated value of the angularvelocity) and is outputted.

The shaking correcting module 50 moves the shift lens 58 in accordancewith this control value, and compensates the tilting of the optical axisof the lens 12 due to the camera shaking.

Namely, due to camera shaking arising, the optical axis of the lens 12tilts with respect to the subject of photographing. The position of theimage of the subject of photographing, which is imaged on the imagepickup element 40, thereby changes.

At the shaking correcting module 50, the tilting due to the camerashaking is detected by the gyro sensor 52 (the vertical angular velocitysensor 52A and the horizontal angular velocity sensor 52B). By movingthe shift lens 58 in accordance with the detected tilting, the tiltingof the optical axis of the lens 12 with respect to the subject ofphotographing is compensated, and no substantial offset arises in theposition of the image of the subject of photographing which is imaged onthe image pickup element 40.

On the other hand, when vibration due to camera shaking arises at thehousing 38, the gyro sensor 52 outputs signals corresponding to thedirection of the vibration and the magnitude of the vibration. Further,after the shaking correcting module 50 carries out integrationprocessing on the output signals of the gyro sensor 52, the shakingcorrecting module 50 computes a control value on the basis of theresults of integration. The shaking correcting module 50 outputs thecomputed control value to the lens driving circuit 56 as the correctionamount. On the basis of this control value, the lens driving circuit 56drives an actuator (not shown), and thereby moves the shift lens 58.

The above respective processings require no small amount of time, andthis time will become the phase delay with respect to the shaking(vibration) of the housing.

Namely, as shown by the solid lines in FIG. 4, with respect to theshaking (the vibration of the housing), in addition to a time (time t₁)until the signal detection output (angular velocity output) from thegyro sensor 52, a time (time t₂) of integration processing (timeintegration) which uses the detected angular velocity and is carried outat the integration computing section 64, and a time (time t₃) needed forcomputation and output of the correction amount (control value) based onthe integration results which is carried out at the correction amountcomputing section 66, there are added a circuit delay (time t₄) spent atthe time until the shift lens 58 is actually driven on the basis of thecontrol value, and the like, and a phase lag thereby exists. Such aphase lag (delay time α) can be determined in advance for each digitalcamera 10.

Thus, the correction amount computing section 66 computes the controlvalue while taking the phase lag (delay time α) into consideration.Specifically, the shaking correcting module 50 outputs the control valueat a time (control time ts) interval (control cycle) which is set inadvance. At the correction amount computing section 66, the integratedvalue of the previous time is stored, and the amount of change in theintegrated value per unit time is computed from the control time and thedifference in the integrated value of the previous time and theintegrated value of the current time. By using this amount of change,the control time ts and the delay time (phase lag) α, an addition valuewith respect to the integrated value is computed. By adding the computedaddition value to the integrated value of the current time, a controlvalue which is accelerated by an amount corresponding to the phase lagcan be obtained.

Namely, given that the delay time at the shaking correcting module 50,which is the phase lag arising at the shaking correcting module 50, isdelay time α (sec), the control time is ts (sec), the integrated valueof the current time which is integrated at the integration computingsection 64 is I_((n)), and the integrated value of the previous time isI_((n-1)), an amount of change Δβ of the integrated value isΔβ=I _((n)) −I _((n-1)).From this, in consideration of the phase lag (delay time α) per controltime ts, an integrated value Is_((n)), which is used in computing anactual control value C_((n)), is computed.Is _((n))=Δβ_((n))×(α−ts)/ts+I _((n))

Namely, by carrying out differentiation processing in consideration ofthe phase lag and the amount of change in the integrated value, thecontrol value C_((n)) at the time of driving the shift lens 56 can beset by using the integrated value Is_((n)) which is obtained byaccelerating the integrated value I_((n)). At this time, the coefficient(delay coefficient) is set on the basis of the delay time α and thecontrol time ts.

In this way, as shown by the dashed lines in FIG. 4, at the shakingcorrecting module 50 provided at the digital camera 10, no phase lagarises in the corrected output with respect to at least the vibration ofthe housing, and by using this corrected output (the control valueC_((n))), the phase lag can be reliably suppressed.

Here, the flow of processings at the shaking correcting module 50 willbe described with reference to FIG. 5. This flowchart is executed, forexample, due to the power switch 18 being turned on, and thephotographing switch 22 being operated, and a photographing mode such asstatic image mode or dynamic image mode or the like being set. In firststep 100, initial setting, such as the resetting of an initial value atthe time of carrying out time integration of the angular velocity, orthe like is carried out.

Note that, at the integration computing section 64, the time integratedvalue (integrated value) of the angular velocity is stored in anunillustrated memory, and is used in computing the control value at thetime of carrying out the next shaking correction. Further, thisflowchart ends due to the power source switch 18 being turned off, ordue to the mode being switched to the playback mode by operation of theplayback switch 24.

When the initial setting is completed, at the interval of the controltime ts which is set in advance, the processings from step 102 on arecarried out, and the shaking correction processing based on thevibration of the housing 38, such as camera shaking or the like, isexecuted.

In step 102, the output signals from the gyro sensor 52 are read out.Due to movement such as shaking or the like arising at the housing 38 ofthe digital camera 10, the gyro sensor 52 outputs signals correspondingto the vertical direction and the horizontal direction angularvelocities thereof.

In next step 104, the integrated value I_((n)) is computed by carryingout time integration with respect to the detected signals of the gyrosensor 52. In step 106, the amount of change Δβ of the integrated valueis computed. Namely, by subtracting the integrated value I_((n-1)) ofthe previous time from the integrated value I_((n)), the amount ofchange Δβ in the angular velocity during the control time ts iscomputed. This amount of change Δβ is a differential value.

Thereafter, in step 108, the addition value with respect to theintegrated value I_((n)) is computed from the differential value (theamount of change Δβ) and the delay coefficient which is determined bythe delay time α and the control time ts. By adding the computedaddition value to the integrated value I_((n)), the control valueC_((n)) is computed (step 110).

Due to the control value C_((n)), which is computed in this way, beingoutputted to the lens driving circuit 56 (step 112), shaking correctionbased on the control value C_((n)) is carried out. Note that if noshaking arises, the control value C_((n)) is zero, and therefore,driving of the shift lens 58 is stopped.

In FIG. 6, an example of angular displacement of the optical axis of thelens 12 due to vibration (shaking) of the housing 38 is shown by thesolid line. Here, when the phase lag α arises, with respect to thisshaking, a control value is computed by carrying out only integrationprocessing on the basis of the outputs of the gyro sensor 52. Theangular displacement of the optical axis, at the time of shifting theshift lens 58 on the basis of this computed control value, is shown bythe dashed line. Note that FIG. 6 illustrates, as an example, a case inwhich the phase lag α is greater than the control time ts (ts<α).

Angles r_((n)), r_((n-1)) are the angles of the optical axis of the lens12 at the time of driving the shift lens 58 based on the control valuesC_((n)), C_((n-1)) which are computed from the integrated value I_((n))and the integrated value I_((n-1)), respectively. Note that the actualangular displacement of the optical axis due to the movement of theshift lens 58 is the opposite phase of the angular displacement of theoptical axis due to shaking, but here, they are illustrated as the samephase.

Here, V_(n) is the displacement amount of the angle based on the resultsof detection of the gyro sensor 52 during the period (the control timets) from time t_((n-1)) to time t_((n)), and is computed as a correctiondifferential value. Further, V_(ns) is the displacement amount at thetime when it is assumed that the angular velocity at this time iscontinuous for a time period corresponding to the phase lag α. Here, gis the error (error g) which arises because the actual vibration is notrectilinear.

Namely, the correction value in computation at time t_((n)) is angler_((n)) which is equal to the integrated value I_((n)), but the actualdisplacement angle (angular displacement) of the housing 38 is R_((n))on the solid line without the phase delay α. Accordingly, by making theangular displacement R_((n)), which is to be reached after time α at theangular velocity of the displacement amount V_(n), be the control valueat time t_((n)), the output of the control value is accelerated by timedisplacement amount V_(t)=(α−ts).

In this way, by using the dashed-line curve, which is the control valuesin computation, as a starting point, a displacement amount V_(N) whichis the acceleration vector is added at each control time (each controltime ts), and the solid-line curve, which is the actual displacementangles (angular displacement) of the housing 38, is determinedapproximately.

Given that the displacement amount of the angle based on thedisplacement amount V_(n) is angular displacement amount A₁, and thatthe displacement amount of the angle based on the displacement amountV_(ns) (displacement amount V_(N)) is angular displacement amount A₂, anangular displacement amount A₃, which is the displacement amount of theangle needed in order to conform to the angle corresponding to theactual vibration at time t_((n)) is:A ₃ =A ₂ −A ₁

Namely, the angular displacement amount A₁ is the angular displacementof the optical axis based on the integrated values I_((n)), I_((n-1)),the angular displacement amount A₂ is the angular displacement needed inorder to make the angle of the optical axis appropriate during the timeperiod from time t_((n-1)) to time t_((n)), and the angular displacementamount A₃ is the angular displacement needed in order to make the angleof the optical axis appropriate based on the control value computed fromthe integrated value I_((n)).

On the other hand, at the shaking correcting module 50, the amount ofchange Δβ is computed from the integrated value I_((n)) of the currenttime and the integrated value I_((n-1)) of the previous time. Bymultiplying (α/ts) which is the delay coefficient by this amount ofchange, an addition value A is computed.

When the time becomes time t_((n)) from time t_((n-1)), in order tocarry out precise shaking correction, the optical axis of the lens 12must become angle R_((n)) by moving the shift lens 58.

From this, it suffices for an integrated value Is_((n)), by which it ispossible to obtain the control value C_((n))needed in order to return tothe appropriate optical axis by the shift lens 58, to beIs _((n)) =I _((n-1))+Δβ×(α/ts)Namely, it suffices forIs _((n)) =I _((n))+Δβ×(α−ts)/ts

Therefore, by addingA=Δβ×(α−ts)/tsas the addition value A to the integrated value I_((n)), appropriateshaking correction can be carried out regardless of the phase lag α ofthe shaking correcting module 50. In this way, at the correction amountcomputing section 66, only simple processings of four-rule computationare added.

Accordingly, at the shaking correcting module 50 which is provided atthe digital camera 10, by the simple processings of four-rulecomputation only, appropriate shaking correction which corresponds tothe shaking of the housing 38 can be carried out, and it is possible toreliably prevent blurring from arising in the photographed image due toshaking.

Note that the error g arises between the displacement amount V_(ns) andthe angular displacement from time t_((n)) on which is based on theresults of detection of the gyro sensor 52. As mentioned above, thiserror g arises because the actual angular change is not rectilinear.However, in the shaking correcting module 50, this error g does notappear and is not accumulated in the result of correction. Further,because the control time ts is sufficiently short with respect to theperiod of the band (the frequency band) of the shaking signal, in theactual driving of the shift lens 58, the error g does not present anyproblems because it is averaged.

Second Embodiment

The schematic structure of main portions of the shaking correctingmodule 50 relating to a second embodiment are shown in FIG. 7. The gyrosensor 52 has the vertical angular velocity sensor 52A and thehorizontal angular velocity sensor 52B. The vertical angular velocitysensor 52A and the horizontal angular velocity sensor 52B detect theangular velocity in the vertical direction and the angular velocity inthe horizontal direction of the digital camera 10, and output signalscorresponding to the detected angular velocities. Note that, instead ofan angular velocity sensor, an acceleration sensor, an angularacceleration sensor, or the like may be used.

HPFs 60, which damp low-band frequency components from the signalsoutputted from the vertical angular velocity sensor 52A and thehorizontal angular velocity sensor 52B respectively, and amplifiercircuits (Amp) 62, which amplify the signals which have passed throughthe HPFs 60, are provided at the gyro sensor 52. In this way, the gyrosensor 52 outputs angular velocity signals with respect to the verticaldirection and the horizontal direction, in which the DC components aresuppressed. Note that, provided that the gyro sensor 52 can outputangular velocity signals corresponding to the detection signals of theangular velocity sensors, the gyro sensor 52 is not limited to this, andan arbitrary structure can be applied thereto.

On the other hand, an A/D converter 64 which converts the angularvelocity signals inputted from the gyro sensor 52 into a digital signal,and an integration computation section 66 and a control voltageconverting section 68 which are formed by a microcomputer (not shown),are provided at the correction computing section 54.

The integration computation section 66 time integrates the angularvelocity signal inputted from the A/D converter 64 at a samplinginterval which is set in advance. An integrated value corresponding tothe angle of the optical axis is thereby obtained.

The integrated value outputted from the integration computation section66 is inputted to the control voltage converting section 68. At thecontrol voltage converting section 68, a control voltage (control value)is set on the basis of the integrated value, and the set control valueis outputted to the lens driving circuit 56.

The lens driving circuit 56 drives the unillustrated actuator inaccordance with this control value, and moves the shift lens 58 in thevertical direction and the horizontal direction.

At the shaking correcting module 50, the tilting of the optical axis ofthe lens 12, which arises due to the shaking of the housing 38, iscompensated by tilting of the optical axis which arises due to themoving of the shift lens 58. In this way, positional offset does notarise in the image of the subject of photographing which is imaged onthe image pickup element 40.

On the other hand, the angular velocity signals outputted from the gyrosensor 52 contain a noise component and a DC component. The outputsignals of the angular velocity sensors 52A, 52B drift greatly due tothe DC components in particular, and there are cases in whichappropriate correction is difficult due to this drift.

Namely, as shown in FIG. 8A, when no drift arises in the angularvelocity signal outputted from the gyro sensor 52, the signal has anamplitude of a predetermined range which is centered around a prescribedcentral value. (The upper and lower limits of the amplitude of theangular velocity signal are shown by the two-dot chain lines in FIGS. 8Athrough 8C.)

In contrast, if drift (e.g., the signal shown by the solid line in FIG.8B) is included in the angular velocity signal outputted from the gyrosensor 52, the range of the amplitude of the angular velocity signalchanges. As shown in FIG. 8C, when the angular velocity is integrated byusing the fixed central value as a reference, and camera shakingcorrection is carried out on the basis of the results of integration, alarge error arises, and blurring of the photographed image cannot besuppressed.

Namely, as shown in FIG. 9, with respect to the original angularvelocity signal (shown by the two-dot chain line in FIG. 9), a driftcomponent (shown by the dashed line in FIG. 9) is contained in theangular velocity signal. Therefore, the angular velocity signal which isoutputted from the gyro sensor 52 in actuality differs from the actualangular velocity due to the drift component, as shown by the solid linein FIG. 9.

Accordingly, when camera shaking correction is carried out on the basisof the angular velocity signals outputted from the gyro sensor 52, alarge error arises, and there are cases in which the blurring of thephotographed image is increased.

In order to prevent such an error from arising, by making the centralvalue (hereinafter called “reference value”) follow in accordance withthe drift, the angular velocity signal of FIG. 8A can be extracted fromthe angular velocity signal of FIG. 8B, and appropriate camera shakingcorrection which corresponds to the output signals of the angularvelocity sensors 52A, 52B is possible.

In order to carry this out, as shown in FIG. 7, a filter processingsection 70 is provided at the shaking correcting module 50 applied tothe second embodiment. This filter processing section 70 may bestructured by hardware, or may be structured by software which isexecuted at an unillustrated microcomputer.

FIG. 10A shows a filter circuit 72 which is an example of the filterprocessing section 70 which is structured by hardware.

A register 74 of a predetermined transfer coefficient n is provided atthe filter circuit 72. An angular velocity signal is inputted as aninput signal to the register 74. Further, the transfer coefficient n isgiven in the range 0<n<1.

A subtractor 76 is provided at the filter circuit 72. A differencesignal of the output signal of the register 74 from the input signal, isoutputted as detected output. At the filter circuit 72, this detectedoutput is to be a corrected angular velocity signal.

The filter circuit 72 has a positive/negative judging section 78, apositive/negative reversing control section 80, and an adder 82. Thepositive/negative judging section 78 judges whether an output signal(output signal value) outputted from the subtractor 76 is positive ornegative, and outputs the results of judgment to the positive/negativereversing control section 80.

A filter coefficient, which is set in advance for each gyro sensor 52,is inputted as a constant value to the positive/negative reversingcontrol section 80. On the basis of the results of judgment of thepositive/negative judging section 78, the positive/negative reversingcontrol section 80 reverses the constant value, and outputs it to theadder 82.

Further, an input signal value is inputted to the adder 82, and theconstant value is thereby added to the input signal value, and the sumis inputted to the register 74.

At the positive/negative reversing control section 80, due to a signal,which has been judged to be positive at the positive/negative judgingsection 78 being inputted, the constant value is added to the inputsignal. When it is judged to be negative, the sign of the constant valueis reversed such that the constant value is subtracted from the inputsignal.

Namely, when the output value of the register 74 (i.e., reference value)is smaller than the input signal value, a signal value, in which theconstant value is added to the input signal value, is inputted to theregister 74. When the output value of the register 74 is greater thanthe input signal value, a signal, in which the constant value issubtracted from the input signal value, is inputted to the register 74.

In this way, at the filter circuit 72, the output value of the register74 is a reference value, and by subtracting the reference value from theinput signal value, an angular velocity signal value, on which driftcorrection has been carried out, is outputted as the output signalvalue.

An example of an input signal inputted to the filter circuit 72 is shownin FIG. 10B. A summary of changes in the reference value with respect tothe input signal of FIG. 10B is shown in FIG. 10C.

As shown in FIGS. 10B and 10C, at the filter circuit 72, if the inputsignal is larger than the central point of the signal, the referencevalue is gradually made larger (increased) at a predetermined incline.Further, if the input signal falls below the central point of thesignal, the reference value is gradually made smaller (decreased). Thereference value at this time varies at an incline which corresponds to aconstant value.

The constant value is determined for each digital camera 10 by carryingout testing, so that the drift is eliminated precisely from the angularvelocity signals outputted from the gyro sensor 52.

A filter circuit 84, which is an example of a filter circuit used ingeneral camera shaking correction, is shown in FIG. 11A. At this filtercircuit 84, the reference value is made to follow the input signalvalue, by using a filter coefficient α which is set in advance and(1−the filter coefficient), and without using results of comparison ofthe input signal value and the reference value. Further, FIG. 11B showsan example of an input signal which is the same as FIG. 10B. FIG. 11C,which corresponds to FIG. 10C, shows changes in the reference valuecorresponding to this input signal.

Here, the results of testing using the filter circuit 72 are shown inFIGS. 12A through 12C. As a comparative example, the results of similartesting using the filter circuit 84 are shown in FIGS. 13A through 13C.

Note that, in FIGS. 12A through 12C and in FIGS. 13A through 13C, thereference value is denoted by BASE, and SIGNAL indicates the inputsignal, and DETECT indicates the output signal. Time is on thehorizontal axis, and voltage is on the vertical axis. Further, in FIGS.12A and 13A, the period of the input signal is 32 msec, in FIGS. 12B and13B, the period of the input signal is 64 msec, and in FIGS. 12C and13C, the period of the input signal is 128 msec.

As shown in FIGS. 13A through 13C, in a case in which the filter circuit84 is used, the reference value varies periodically in accordance withthe input signal, and offset in the phases arises between the inputsignal and the reference value. Therefore, offset in the phases arisesbetween the input signal and the output signal. In particular, when thefrequency is long as shown in FIG. 13C, the offset in the phases also isgreat.

Namely, in the filter circuit 82, the reference value includes not onlya DC component, but also a frequency component corresponding to theperiod of the input signal. Therefore, when the reference value isextracted from the input signal, the error between the input signal andthe output signal is large, and appropriate shaking correction isdifficult.

In contrast, as shown in FIGS. 12A through 12C, there is little changein the reference value at the filter circuit 72.

Therefore, when the filter circuit 72 is used, offset in the phases doesnot arise between the input signal and the output signal. Namely, it ispossible to extract only the drift component (the DC component).

Accordingly, it is possible to obtain an output signal in which drift ofthe input signal due to the drift component is suppressed, andappropriate camera shaking correction can be carried out by removing thedrift from the angular velocity signals outputted from the gyro sensor52.

Further, at the filter circuit 72, this is made possible by the simplestructure of merely addition and subtraction of a constant value whichis set in advance.

An example using the filter circuit 72 has been described heretofore,but processing in accordance with software can be also applied.

The flow of processings in this case is shown in FIG. 14. This flowchartis executed, for example, at the time when the digital camera 10 is setin the photographing mode, and initial setting is carried out at first.

In this initial setting, in step 100, the angular velocity signal(angular velocity signal value) outputted from the gyro sensor 52 isread-in as an input signal (input signal value). In next step 102, aninitial value of the reference value is set from the input signal valuewhich is read-in.

Thereafter, a value, which is obtained by subtracting the referencevalue from the input signal value, is outputted as an output signalvalue (output signal) (step 104). Note that this initial setting may beomitted, and a value which is set in advance may be used as thereference value.

When the initial setting is carried out in this way, the steps from step106 on are repeatedly executed at a predetermined sampling interval (thecontrol time interval of the camera shaking correction). In step 106,the input signal value outputted from the gyro sensor 52 is read. Innext step 108, the input signal value is compared with the referencevalue, and it is judged whether or not the input signal value is greaterthan the reference value.

Here, if the input signal is greater than the output signal, thedetermination in step 108 is affirmative, and the routine moves on tostep 110 where a constant value which is set in advance is set as anaddition value. Next, in step 112, the set addition value is added tothe reference value so as to update the reference value.

Thereafter, the routine moves on to step 114 where an output signalvalue is computed by subtracting the reference value from the inputsignal value.

Further, if the reference value is larger than the input signal value,the determination in step 108 is negative, and the routine proceeds tostep 116. In step 116, it is confirmed whether or not the input signalvalue is lower than the reference value, and if the determination isaffirmative, the routine moves on to step 118.

In step 118, the constant value is set as a subtraction value. In nextstep 120, by subtracting the constant value from the reference value,the reference value is updated.

Thereafter, the routine proceeds to step 114, where the output signalvalue is computed from the input signal value and the reference value.

Further, when the input signal value and the reference signal value arethe same, the determination in step 116 is negative, and the routinemoves on to step 114. In this way, without updating the reference value,computation of the output signal value using this reference value iscarried out.

By carrying out these processings, an output signal, in which the driftcomponent is precisely removed from the input signal, can be obtained.By using this output signal as the angular velocity signal detected atthe gyro sensor 52, optimal shaking correction utilizing the shift lens58 can be carried out.

Third Embodiment

A third embodiment of the present invention will be described next. Notethat the basic structure of the third embodiment is the same as theabove-described second embodiment. In the third embodiment, parts whichare the same as in the second embodiment are denoted by the samereference numerals, and description thereof is omitted.

The schematic structure of a shaking correcting module 50A applied tothe third embodiment is shown in FIG. 15.

In addition to the A/D converter 64, the integration processing section66, and the control voltage converting section 68 at a correctioncomputing section 54A, the shaking correcting module 50A also has afilter processing section 86 between the integration computing section66 and the control voltage converting section 68.

At the filter processing section 86, the drift component contained inthe angular velocity signal is removed from the integrated value whichis obtained by integrating the angular velocity signal outputted fromthe gyro sensor 52. In this way, at the shaking correcting module 50A,it is possible to carry out appropriate shaking correction processingbased on an angular velocity signal which does not include a driftcomponent.

A filter circuit 88, which is an example of a filter circuit provided atthe filter processing section 86, is shown in FIG. 16A. The filtercircuit 88 is structured to include a register 90, a subtractor 92, anadder 94, a positive/negative judging section 78A and apositive/negative reversing control section 80A.

An integrated value (input integrated value), which is an integratedvalue obtained by carrying out integration processing at the integrationprocessing section 66, is inputted to the filter circuit 88 as an inputsignal (input signal value). A reference value outputted from theregister 90 is subtracted from this integrated value, and an integratedvalue used in setting the control value (control voltage) for the timeof driving shift lens 56 is outputted.

An output signal value (output integrated value) of the subtractor 92 isinputted to the positive/negative judging section 78A. Thepositive/negative judging section 78A judges the sign of the outputintegrated value outputted from the filter circuit 88.

On the other hand, a signal corresponding to the results of judgment ofthe positive/negative judging section 78A, and a constant value(correction constant value) which is set in advance and serves as anaddition/subtraction constant used in addition and subtraction, areinputted to the positive/negative reversing control section 80A.

At the positive/negative reversing control section 80A, when the outputintegrated value outputted from the filter circuit 88 is negative,setting is carried out such that the correction constant value is usedas a subtraction constant value. When the output integrated value ispositive, setting is carried out such that the correction constant valueis used as an addition constant value.

The correction constant, whose positive/negative sign is set at thepositive/negative reversing control section 80A, is added to orsubtracted from the reference value, and the result is inputted to theregister 90. In this way, at the filter circuit 88, the reference valueoutputted from the register 90 is made t be a divergent correction value(and is hereinafter called “divergent correction value”).

For the transfer coefficient n of the register 90 and the correctionconstant value, measurement of the integrated value outputted from thefilter circuit 88 is carried out by carrying out testing or the like inadvance, and values which can move the shift lens 58 appropriately withrespect to the angular velocity detected by the gyro sensor 52 are set.

At the filter circuit 88, by using this correction constant value, thereference value outputted from the register 90 is the divergentcorrection value, and it is possible to prevent the integrated valuewhich is outputted from the filter circuit 88 from converging in a highfrequency region. Moreover, the drift components, which are included inthe angular velocity signals outputted from the gyro sensor 52, do notappear in the integrated value which is used in setting the controlvalue for driving the shift lens 58.

FIG. 16B shows an example of an input signal (an example of thevariation of the input integrated value) inputted to the filter circuit88, and FIG. 16C shows a summary of changes in the divergent correctionvalue with respect to the input signal of FIG. 16B.

As shown in FIGS. 16B and 16C, at the filter circuit 88, when the inputintegrated value which is the input signal is larger than the centralpoint of the signal, the divergent correction value gradually becomeslarger (increases) at a predetermined incline. Further, if the inputsignal falls lower than the central point of the signal, the divergentcorrection value gradually becomes smaller (decreases). The divergentcorrection value at this time varies at an incline corresponding to theaddition/subtraction constant value (the correction constant).

A filter circuit 96, which is an example of a filter circuit of ageneral structure which suppresses divergence in the integrated value atthe time of carrying out camera shaking correction, is shown in FIG.17A. In this filter circuit 96, a divergent correction value isoutputted from a register 98 by using a filter coefficient which is setin advance. At this time, at the filter circuit 96, the divergentcorrection value is made to follow the input signal, without usingresults of comparison of the input signal and the divergent correctionvalue. Further, an example of an input signal which is the same as FIG.16B is shown in FIG. 17B. Changes in the reference value (the divergentcorrection value) with respect to the input signal are shown in FIG. 17Cwhich corresponds to FIG. 16C.

As can be understood by comparing FIGS. 16B, 16C and FIGS. 17B, 17C,when the filter circuit 88 is used, effects which are equivalent tothose of the filter circuit 72 which is applied to thepreviously-described second embodiment can be obtained. Accordingly,also at the shaking correcting module 50A which removes the driftcomponent from the integrated value of the angular velocity signals,appropriate camera shaking correction using the gyro sensor 52 ispossible.

Further, at the filter processing section 86 as well, processing bysoftware can be utilized instead of the filter circuit 88.

FIG. 18 shows the flow of processings in this case. This flowchart isexecuted at a predetermined sampling interval (the control time intervalof the camera shaking correction). In initial step 130, an integratedvalue inputted from the integrated processing section, is read as aninput integrated value. In next step 132, it is judged whether the inputintegrated value is positive or not.

Here, if the input integrated value is positive, the determination instep 132 is affirmative, and the routine moves on to step 134 where acorrection constant which is set in advance is set as a subtractionvalue. Then, in step 136, by adding the set subtraction value to thedivergent correction value (i.e., by subtracting the correction constantfrom the divergent correction value), the divergent correction value isupdated.

Thereafter, the routine moves on to step 138 where, due to the divergentcorrection value being subtracted from the input integrated value, anoutput integrated value is computed.

On the other hand, if the input integrated value is not positive, thedetermination in step 132 is negative, and the routine moves on to step140 where it is confirmed whether or not the input integrated value isnegative. If the input integrated value is negative, the determinationin step 140 is affirmative, and the routine moves on to step 142.

In step 142, the correction constant is set as an addition value, and innext step 144, due to the correction constant being added to thedivergent correction value, the divergent correction value is updated.

Thereafter, the routine moves on to step 138 where the output integratedvalue is computed from the input integrated value and the divergentcorrection value.

Moreover, when the input integrated value is zero, the determinations instep 132 and step 140 are negative, and the routine proceeds to step138. In this way, computation of the output integrated value using thedivergent correction value is carried out, without the divergentcorrection value being updated.

By carrying out such processing, while the integrated value computed atthe integration processing section 66 is prevented from diverging, anoutput integrated value, which is equivalent to the drift componentbeing precisely removed from the angular velocity signal, can beobtained. By using this output integrated value, optimal shakingcorrection using the shift lens 58 can be carried out.

Note that the above-described embodiments are not intended to limit thestructure of the present invention. For example, in the embodiments, thedigital camera (digital still camera) 10 is described as an example, butthe present invention can be applied to a digital still camera of anarbitrary structure provided that it is equipped with an optical-typecamera shaking correcting function.

Further, the present invention is not limited to a digital still camera,and can be applied to an image pickup device of an arbitrary structurewhich generates image data corresponding to an image of a subject ofphotographing by imaging, onto an image pickup element, light which iscollected by a lens, such as a digital video camera or the like.

1. A method of correcting camera shaking which, in an image pickupdevice outputting image data corresponding to an image of a subject ofphotographing which is imaged by a lens on an image pickup element ofthe device, corrects, by movement of a lens, tilting of an optical axisdue to shaking of a housing of the device, the method comprising:detecting, at a predetermined control time interval, an angular velocityat a time when shaking of the housing arises; on the basis of a timeintegrated value of the detected angular velocity, setting an amount ofmovement of the lens which compensates the tilting of the optical axisdue to shaking of the housing, the setting including adding an additionvalue, which is based on a difference between a time integrated value ofthe current time and a time integrated value of a previous time and on adelay coefficient set from a phase delay and the control time, to thetime integrated value of the current time; and moving the lens on thebasis of a control value obtained from results of the adding.
 2. Adevice for correcting camera shaking which corrects, by movement of alens, tilting of an optical axis due to shaking of a housing of an imagepickup device which outputs image data corresponding to an image of asubject of photographing which is imaged by a lens on an image pickupelement of the image pickup device, the device for correcting camerashaking comprising: a vibration detecting section detecting shaking ofthe housing, and outputting a signal corresponding to the shaking; anintegration processing section reading a detection signal of thevibration detecting section at a predetermined control time interval,and computing a time integrated value; a computing section storing atime integrated value of the integration processing section, andcomputing an addition value for the time integrated value, on the basisof a difference between the time integrated value and a time integratedvalue of a previous time, and a delay coefficient set from a phase delayand the control time; a setting section setting an amount of movement ofthe lens from the integrated value to which the addition value has beenadded by the computing section; and a lens driving section moving theoptical axis of the lens on the basis of the amount of movement set bythe setting section.
 3. The device for correcting camera shaking ofclaim 2, wherein the vibration detecting section is a gyro sensor.
 4. Animage pickup device outputting image data corresponding to an image of asubject of photographing which is imaged by a lens on an image pickupelement of the device, the image pickup device comprising: a vibrationdetecting section detecting shaking of a housing which houses the lensand the image pickup element, and outputting a signal corresponding tothe shaking; an integration processing section reading a detectionsignal of the vibration detecting section at a predetermined controltime interval, and computing a time integrated value; a computingsection storing a time integrated value of the integration processingsection, and computing an addition value for the time integrated value,on the basis of a difference between the time integrated value and atime integrated value of a previous time, and a delay coefficient setfrom a phase delay and the control time; a setting section setting anamount of movement of the lens from the integrated value to which theaddition value has been added by the computing section; and a lensdriving section moving an optical axis of the lens on the basis of theamount of movement set by the setting section.
 5. The image pickupdevice of claim 4, wherein the vibration detecting section is a gyrosensor.
 6. A device for correcting camera shaking provided at an imagepickup device which outputs image data corresponding to a photographedimage which has passed through a lens housed in a housing of the imagepickup device and which is imaged on an image pickup element of theimage pickup device, the device for correcting camera shakingcomprising: an angular velocity detecting section detecting an angularvelocity due to shaking arisen at the housing; an integration computingsection computing an integrated value corresponding to a change in anangle of an optical axis of the lens due to shaking, by time integratingat a predetermined time interval an angular velocity signal outputtedfrom the angular velocity detecting section; a control value settingsection which, on the basis of an integrated value outputted from theintegration computing section, sets a control value for obtaining acorrection angle needed in order to compensate tilting of the opticalaxis of the lens due to the shaking; a lens driving section which, onthe basis of the control value set by the control value setting section,drives the lens so as to tilt the optical axis of the lens; and a filterprocessing section which extracts a reference value from the angularvelocity signal detected by the angular velocity detecting section, andoutputs a difference between the detected angular velocity signal andthe reference value to the integration computing section as a correctedangular velocity signal, the filter processing section extracting thereference value from an angular velocity signal to which a presetconstant value has been added or subtracted on the basis of results ofcomparison of the reference value and an angular velocity signalinputted from the angular velocity detecting section.
 7. The device forcorrecting camera shaking of claim 6, wherein the filter processingsection adds the constant value to the angular velocity signal, when alevel of the angular velocity signal is greater than a level of thereference value, and subtracts the constant value from the angularvelocity signal, when the level of the angular velocity signal issmaller than the level of the reference value.
 8. The device forcorrecting camera shaking of claim 6, wherein the angular velocitydetecting section is a gyro sensor.
 9. The device for correcting camerashaking of claim 6, wherein the filter processing section is a filtercircuit comprising: a register; a subtractor to which are inputtedoutput from the register and the angular velocity signal detected by theangular velocity detecting section; a positive/negative judging sectionto which an output signal from the subtractor is inputted, and whichoutputs results of judgment on a positive/negative sign of the outputsignal from the subtractor; a positive/negative reversing controlsection to which output from the positive/negative judging section andthe constant value are inputted, and which reverses a positive/negativesign of the constant value on the basis of the output from thepositive/negative judging section and outputs the constant value whosepositive/negative sign has been reversed; and an adder to which theangular velocity signal detected by the angular velocity detectingsection and output from the positive/negative reversing control sectionare inputted, and output from the adder is inputted to the register, andthe register outputs the input to the subtractor as a reference value,and the subtractor outputs results of computation thereof as a correctedangular velocity signal.
 10. A device for correcting camera shakingprovided at an image pickup device which outputs image datacorresponding to a photographed image which has passed through a lenshoused in a housing of the image pickup device and which is imaged on animage pickup element of the image pickup device, the device forcorrecting camera shaking comprising: an angular velocity detectingsection detecting an angular velocity due to shaking arisen at thehousing; an integration computing section computing an integrated valuecorresponding to a change in an angle of an optical axis of the lens dueto shaking, by time integrating at a predetermined time interval anangular velocity signal outputted from the angular velocity detectingsection; a control value setting section which, on the basis of anintegrated value outputted from the integration computing section, setsa control value for obtaining a correction angle needed in order tocompensate tilting of the optical axis of the lens due to the shaking; alens driving section which, on the basis of the control value set by thecontrol value setting section, drives the lens so as to tilt the opticalaxis of the lens; and an integrated value filter processing sectionwhich is provided at the control value setting section, and whichcorrects an integrated value used in setting the control value by addingor subtracting a preset constant value to or from the integrated valuein accordance with a positive/negative sign of the integrated valueoutputted from the integration computing section.
 11. The device forcorrecting camera shaking of claim 10, wherein the integrated valuefilter processing section subtracts the constant value from theintegrated value when the integrated value is positive, and adds theconstant value to the integrated value when the integrated value isnegative.
 12. The device for correcting camera shaking of claim 10,wherein the angular velocity detecting section is a gyro sensor.
 13. Thedevice for correcting camera shaking of claim 10, wherein the integratedvalue filter processing section is a filter circuit comprising: aregister; a subtractor to which are inputted output from the registerand an integrated value outputted from the integration computingsection; a positive/negative judging section to which output from thesubtractor is inputted, and which outputs results of judgment on apositive/negative sign of the output from the subtractor; apositive/negative reversing control section to which output from thepositive/negative judging section and the constant value are inputted,and which reverses a positive/negative sign of the constant value on thebasis of the output from the positive/negative judging section andoutputs the constant value whose positive/negative sign has beenreversed; and an adder to which the angular velocity signal detected bythe angular velocity detecting section and output from the register areinputted, and output from the adder is inputted to the register, and theregister outputs the input to the subtractor, and the subtractor outputsresults of computation thereof as a corrected integrated value.
 14. Animage pickup device which outputs image data corresponding to aphotographed image which has passed through a lens housed in a housingof the device and which is imaged on an image pickup element of thedevice, the image pickup device comprising: an angular velocitydetecting section detecting an angular velocity due to shaking arisen atthe housing; a filter processing section which extracts a referencevalue from the angular velocity signal detected by the angular velocitydetecting section, and outputs a difference between the detected angularvelocity signal and the reference value as a corrected angular velocitysignal, the filter processing section extracting the reference valuefrom an angular velocity signal to which a preset constant value hasbeen added or subtracted on the basis of results of comparison of thereference value and an angular velocity signal inputted from the angularvelocity detecting section; an integration computing section computingan integrated value corresponding to a change in an angle of an opticalaxis of the lens due to the shaking, by time integrating at apredetermined time interval the angular velocity signal corrected by thefilter processing section; a control value setting section which, on thebasis of the integrated value outputted from the integration computingsection, sets a control value for obtaining a correction angle needed inorder to compensate tilting of the optical axis of the lens due to theshaking; and a lens driving section which, on the basis of the controlvalue set by the control value setting section, drives the lens so as totilt the optical axis of the lens.
 15. The image pickup device of claim14, wherein the filter processing section adds the constant value to theangular velocity signal, when a level of the angular velocity signal isgreater than a level of the reference value, and subtracts the constantvalue from the angular velocity signal, when the level of the angularvelocity signal is smaller than the level of the reference value. 16.The image pickup device of claim 14, wherein the filter processingsection is a filter circuit comprising: a register; a subtractor towhich are inputted output from the register and the angular velocitysignal detected by the angular velocity detecting section; apositive/negative judging section to which an output signal from thesubtractor is inputted, and which outputs results of judgment on apositive/negative sign of the output signal from the subtractor; apositive/negative reversing control section to which output from thepositive/negative judging section and the constant value are inputted,and which reverses a positive/negative sign of the constant value on thebasis of the output from the positive/negative judging section andoutputs the constant value whose positive/negative sign has beenreversed; and an adder to which the angular velocity signal detected bythe angular velocity detecting section and output from thepositive/negative reversing control section are inputted, and outputfrom the adder is inputted to the register, and the register outputs theinput to the subtractor as a reference value, and the subtractor outputsresults of computation thereof as a corrected angular velocity signal.17. An image pickup device which outputs image data corresponding to aphotographed image which has passed through a lens housed in a housingof the device and which is imaged on an image pickup element of thedevice, the image pickup device comprising: an angular velocitydetecting section detecting an angular velocity due to shaking arisen atthe housing; an integration computing section computing an integratedvalue corresponding to a change in an angle of an optical axis of thelens due to shaking, by time integrating at a predetermined timeinterval an angular velocity signal outputted from the angular velocitydetecting section; an integrated value filter processing section whichcorrects the integrated value by adding or subtracting a preset constantvalue to or from the integrated value, in accordance with apositive/negative sign of the integrated value outputted from theintegration computing section; a control value setting section which, onthe basis of the integrated value corrected by the integrated valuefilter processing section, sets a control value for obtaining acorrection angle needed in order to compensate tilting of the opticalaxis of the lens due to the shaking; and a lens driving section which,on the basis of the control value set by the control value settingsection, drives the lens so as to tilt the optical axis of the lens. 18.The image pickup device of claim 17, wherein the integrated value filterprocessing section subtracts the constant value from the integratedvalue when the integrated value is positive, and adds the constant valueto the integrated value when the integrated value is negative.
 19. Theimage pickup device of claim 17, wherein the integrated value filterprocessing section is a filter circuit comprising: a register; asubtractor to which are inputted output from the register and anintegrated value outputted from the integration computing section; apositive/negative judging section to which output from the subtractor isinputted, and which outputs results of judgment on a positive/negativesign of the output from the subtractor; a positive/negative reversingcontrol section to which output from the positive/negative judgingsection and the constant value are inputted, and which reverses apositive/negative sign of the constant value on the basis of the outputfrom the positive/negative judging section and outputs the constantvalue whose positive/negative sign has been reversed; and an adder towhich the angular velocity signal detected by the angular velocitydetecting section and output from the register are inputted, and outputfrom the adder is inputted to the register, and the register outputs theinput to the subtractor, and the subtractor outputs results ofcomputation thereof as a corrected integrated value.